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      Effect of Elevated Calcium Levels on Segmental Tubular Sodium Reabsortion in Normal Man

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          Abstract

          The aim of the present study was to assess the effect of calcium infusion on segmental tubular reabsorption in humans using lithium clearance, along with creatinine and free water clearances during maximal water diuresis. In 8 healthy volunteers, a 20-min 5 mg/kg calcium infusion that increased serum calcium levels from 2.27 ± 0.07 to 2.87 ± 0.07 mmol/l (p < 0.01) was followed by a 60-min 3 mg/kg infusion for maintenance. During the experimental period, blood pressure did not change. Maximal urine flow increased from 15.6 ± 2.4 to 20.8 ± 2.8 ml/min (p < 0.01), while clearance of sodium increased from 1.5 ± 0.4 to 3.7 ± 0.9 ml/min (p < 0.001). Lithium clearance showed an increase of 7.4 ml/min, pointing to a suppression of proximal reabsorption. Free water clearance also increased from 11.5 ± 3.7 to 14.4 ± 3.9 ml/min, indicating an increase in TALH reabsorption which was attributed to increased sodium and water reaching this segment. Time control studies showed no significant changes in the parameters measured except for potassium excretion. Potassium excretion during calcium infusion was somewhat lower than during the control studies. The data support the view that an increase in serum calcium concentration leads to a decrease in proximal tubular reabsorption as indicated by lithium clearance while a decrease in reabsorption in the collecting duct could well add to the diuretic properties of calcium.

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          Author and article information

          Journal
          NEF
          Nephron
          10.1159/issn.1660-8151
          Nephron
          S. Karger AG
          1660-8151
          2235-3186
          1996
          1996
          19 December 2008
          : 73
          : 1
          : 63-66
          Affiliations
          aDepartment of Nephrology, Ege University, and bDepartment of Biochemistry, SSK Tepecik Hospital, Izmir, Turkey
          Article
          189001 Nephron 1996;73:63–66
          10.1159/000189001
          8742959
          © 1996 S. Karger AG, Basel

          Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

          Page count
          Pages: 4
          Categories
          Original Paper

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